His impressionistic style was trademark Berkey, and his depiction of hardware was excellent. While not as well-known to fans as many other artists in the field, Berkey was widely admired by his fellow artists; Vincent Di Fate called him "one of the most innovative and influential of science fiction artists."

A frequent movie poster artist, Berkey's film work included The Towering Inferno (1974), Orca (1977), King Kong (1976), and the 1978 re-release of both When Worlds Collide and The War of the Worlds. He also did the pre-production designs for Star Wars.

The Art of John Berkey, in which Berkey’s career is examined in depth, appeared from Paper Tiger in 2003, edited by Jane Frank.